1. Field of the Invention
The invention is based on device for restoring a throttle valve, which is for controlling the combustion air of an internal combustion engine, into a limp-home air position.
2. Description of Prior Art
In the event of a failure of the drive mechanism for the driver on the throttle valve shaft, which drive mechanism is an electric motor, for example, a restoring device of this kind is used to restore the throttle valve into a definite idle position, the so-called limp-home air position or limp-home position, in which a minimal throttle valve opening for the supply of combustion air to the internal combustion engine is assured so that the engine continues to run smoothly at idle speed or at a minimal load.
Due to tolerances in the housing-and driver catch and due to the bending precision of the bent spring ends of the clamping spring, in the limp-home air position, in which the driver catch and the housing catch are disposed radially offset from and approximately congruent to each other, there is a certain rotary play in the throttle valve shaft, which renders a precise regulation impossible in this range.
In a known restoring device disclosed in DE 197 35 046 A1, in order to achieve a rotary play-free embodiment with a definite idle position of the catches in the limp-home air position, oblique catch surfaces are provided on the housing catch and the driver catch. The one spring end of the clamping spring is secured to the oblique catch surfaces on the one side and the other spring end of the clamping spring is secured to the flat catch surfaces extending parallel to the catch axis, on the other side from the housing catch and the driver catch. Because of the oblique catch surfaces, the spring end is supported with half of the respective spring force against the two oblique catch surfaces and thus moves the rotatable driver catch in relation to the catch formed by the spring end on the other side of the housing catch and driver catch.
The restoring device according to the invention has the advantage that the rotary play-free state in the limp-home air position is reliably achieved with technically simple means. The compensation spring can be produced as a simple stamped part and is easy to install. The additional manufacturing costs for producing a reliable play-free state are therefore minimal.